MOS (from the first letters of "Mountain Ocean Sun") burger began in the 1970s and one of its most popular meals at the outset was its "teriyaki burger" which combined a Japanese dish with the American hamburger.

MOS Burger now has over 1300 fast-food restaurants in Japan, with branches overseas in Singapore, Taiwan, Thailand, Indonesia and Hong Kong. The company also operates the 80^C stores, MOS's-C, Mother Leaf, Mamedori, Shanghalichiba and Stefan Grill food outlets.

MOS made over 552 million yen in 2009 and is the second largest fast-food franchise in Japan after its rival McDonalds.

As well as hamburgers, MOS offers hot-dogs, fried chicken, fried potatoes, soup, desserts and a morning-set meal. MOS is also trying to diversify its menu by adding more meals aimed at the health-conscious.

MOS has its HQ in Shinagawa-ku in Tokyo and employs around 900 full-time employees, with the rest of the staff made up of part-time workers.